New computer for Christmas.

Hey, so I've got a budget of around $800, I want a nice gaming computer that'll last me a while. I'd love to play WoW on ultra and SWTOR with decent graphics and no lag. I'd prefer a premade computer, as I don't see the risk of ruining a piece of hardware building a new computer worth saving ~$200 if done correctly. What's the best deal for my money?

If I could buy it from Best Buy, I'd be able to put it on a payment plan and be able to go over the $800 budget. If I had to buy it online, it'd be pretty close to 800 on the dot.

1) What is the best deal for a premade?
2) Does Best Buy rip you off for the specs you get for your money?
3) How much could I save if I built it myself?

Thanks, Bally, but I was really looking for a desktop. You can't upgrade laptops much to keep up with the times. I was looking at several desktops on newegg for $629 (iBuyPower) or a $749 CyberPowerPC.